1. Field of the Invention
The invention relates generally to the field of photography, and in particular to a film cassette containing roll film.
2. Description of the Prior Art
German Offenlegungsschrift DE 4002778 Al, published Aug. 2, 1990, discloses a film cassette wherein a light blocking valve is supported for movement to a closed position for preventing ambient light from entering a cassette shell and an opened position for allowing a filmstrip to be advanced out of the shell. The filmstrip is advanced out of the shell when a spool on which the filmstrip is wound is rotated in an unwinding direction and a film engaging sprocket located between the spool and the light valve is similarly rotated. The spool can be rotated in the unwinding direction even though the light blocking valve is closed. Consequently, the filmstrip may be unwound from the spool and jammed inside the shell.